有关氨基酸旋光性的讨论

问：在高等生物中，尤其是人体内，所含有的蛋白质均由L－型氨基酸构成，但是，据研究表明，随着人体的衰老，机体内一些氨基酸会自发转变为D－型。这种立体议购现象的出现是否是机体开始衰老的一个标志，能否通过降低异构化过程来推迟机体衰老？欢迎大家讨论。

答：有意思，很有可能构型的确蕴涵着丰富的生物学信息。但这个过程能用什么方法才能控制呢？很有意思的命题！

问：怎样识别和分离体内旋光性不同的氨基酸呢？目前来看，HPLC是首选，但是能不能开发一种新的简单快速的检测不同构型的氨基酸，是开展这一方面课题的当务之急。请有在有机化学领域擅长的大侠们思考思考。

答：这是从网页上找到的。希望大家共同参与讨论。

L/D RATIOS OF DISSOLVED COMBINED AMINO ACIDS AS INDICATORS OF DOM QUALITY TO BACTERIA

All protein amino acids are L enantiomers but peptidoglycan in bacterial cell walls has a high content of D amino acids. In marine waters, recalcitrant DOM has a L/D ratio of 3 to 4, compared to ratios of 7 to 8 of fresh DOM. In the present study the L/D ratio of selected dissolved combined amino acids (asp, glu and ala) in water samples from an estuary and from batch cultures of marine bacteria was examined and related to the biological activity. The analyses demonstrated (1) that a high L/D amino acid ratio coincided with a high algal biomass, (2) that bacteria reduced L amino acids in preference to D amino acids, and (3) that estuarine bacteria in stationary growth phase released D amino acids. Thus, L/D ratios of amino acids reflect a balance between production and consumption of both enantiomers. Despite this complex relationship, pronounced seasonal and depth changes of L/D ratios from Roskilde Fjord, Denmark, and the Gulf of Riga, the Baltic Sea, correlated with the primary productivity (increased L/D ratios) and bacterial growth (reduced L/D ratios). Results from the Gulf of Riga suggested that a transiently accumulation of D enantiomers may occur in the summer. More studies are required to understand natural variations of L/D amino acid ratios, but the present results suggest that enantiomer ratios can be a valuable tool for evaluating origin and lability of DOM in natural waters.